Chronic Traumatic Encephalopathy

Proceedings of the Boston University Alzheimer's Disease Center Conference

Andrew E. Budson, Ann C Mckee, Robert C. Cantu, Robert A. Stern

• Publisher: Elsevier
• Year: 2017
• ISBN:
  9780323544269
• Topic: Medicine
• Subtopic: Neurology

Get a thorough, expert overview of the many key facets of chronic traumatic encephalopathy (CTE) with this concise, practical resource by Drs. Andrew E. Budson, Ann C. McKee, Robert C. Cantu, and Robert A. Stern. This easy-to-read reference is based on lectures from Boston University's Alzheimer's Disease Center's November 2016 two-day conference on CTE.

Chapter 1

History of Concussion and Chronic Traumatic Encephalopathy

Robert C. Cantu, and Thomas A. Gennarelli

Abstract

This chapter focuses on the history of concussion and chronic traumatic encephalopathy (CTE) research. It reports the changing definitions of concussion and how this change influences its recognition and reporting. It covers the changing role of grading concussion, return-to-play guidelines, and the current graduated return-to-play protocol. It chronicles the CTE story starting with Marland's 1928 JAMA publication about boxers, the 2005 Omalu publication of CTE in a National Football League football player, Ann McKee's world's largest brain bank series of CTE in all sports, and Bob Stern's seminal work in attempting to detect CTE in the living. Finally, the cogent unanswered questions regarding CTE and the need for increased recognition are discussed.

Keywords

Chronic traumatic encephalopathy; Concussion; Concussion checklist; Return-to-play protocol; Subconcussion

Introduction

Good morning everyone. I guess they have given the oldest person the task of leading off. I will be giving you some history. It is fun for me to be giving this talk because I have lived an awful lot of this history—about 50 plus years in terms of the concussion part of it and a fair amount in regards to the chronic traumatic encephalopathy (CTE) part, which is now being remade by Dr. Ann McKee, Dr. Robert Stern, and the Boston University (BU) group. We are all so thrilled to be a part of this history.

Let me start with a question. How many people think this statement is true: “Today there are more concussions occurring because players are bigger, stronger, and faster”? Or is it that, “There are more concussions today because we are better at recognizing concussions and documenting them”? How many people would think that’s true? How many of you think both of these statements are true? How many people think there is even more to it? I am going to circle back to these questions in a little bit.

Historical Theories of Concussion

Going way back to the 1960s there were a number of theories about concussions. There was a vascular theory that the symptoms that occur after mechanically induced head trauma resulted from the constriction of blood flow to certain areas of the brain. The reticular theory—that the ascending reticular activating system (ARAS) was affected—was popular because prior to the mid-1970s virtually all concussions were diagnosed when there was loss of consciousness. We know that this system—running from the upper cervical cord at C1 up to the thalamus—is what is involved in the wakeful state. So that particular theory of concussion was held in pretty high regard at that point. Most concussions were not athletic concussions; they were mostly involving automobile accidents with high-speed trauma. So concussions at this time usually involved a loss of consciousness. There was a centripetal theory from Ommaya. There was the pontine cholinergic system theory. There were also other theories that, way back in the day 50 plus years ago, had some series advocates. One was related to the fact that after a concussive event and loss of consciousness there is very often what we now believe is a brainstem reflex, and that is abnormal posturing of the athlete with stiffening of their legs and bringing their arms up. This posture isn’t due to a seizure, and we really believe that it is more of a brainstem reflex. Over the years it hasn’t been correlated with the severity of concussion, but way back in the day, people thought it was.

Theories of Concussion

• Vascular: brief ischemia, decreased cerebral blood flow

• Reticular: brainstem site, effect on the ARAS produces loss of consciousness

• Centripetal: a complex variation of reticular

• Pontine cholinergic system: activation of the inhibitory system in the dorsal pons

• Convulsive: symptoms like those of a seizure

Definitions of Concussion

Prior to the mid-1970s, most physicians defined concussion as a loss of consciousness. Then in the mid-1970s into the 1980s concussion became more and more well recognized, and we understood that you don’t have to be unconscious, you just need an alteration of the level of consciousness. So being stunned or concussed or having amnesia would get you into a concussed group without loss of consciousness. Then when we got further into the 1980s there were more and more symptoms of concussion. There were somatic symptoms, including light sensitivity, noise sensitivity, and headaches. There were also mood symptoms, behavior symptoms, and sleep symptoms—when they were traumatically induced, those nonspecific symptoms pretty much became the definition of concussion. More recently, from the year 2000 onward, it has been pretty much any mechanically induced symptoms that have been used to define concussion.

Centripetal Theory of Concussion

In 1974, two neurosurgeons, Ayub Ommaya and Tom Gennarelli, wrote a seminal paper entitled, “Cerebral concussion and traumatic unconsciousness. Correlation of experimental and clinical observations of blunt head injuries.” Published in the journal Brain, it presented the centripetal theory of concussion, many aspects of which have survived to this day. The concept that there are stresses and strains in the brain that are mechanically induced is really what we are working on today to better understand concussion. The centripetal theory also has a part that didn’t stand the test of time; that was that mechanically induced forces would be maximal in the periphery of the brain, and if they were severe enough they would make their way down to the central parts of the brain to the brainstem itself.

Loss of Consciousness

In the late 1990s the American Academy of Neurology came out with their guidel...